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Eyes: How They Work, Anatomy and Common Condition

 The eye is a complex sensory organ that allows us to see the world around us. The eye works by gathering light from the environment and converting it into electrical signals that can be interpreted by the brain. The basic structure of the eye includes the cornea, iris, pupil, lens, retina, and optic nerve. The cornea is the transparent outer layer of the eye that helps to focus incoming light. The iris is the colored part of the eye that regulates the amount of light that enters the eye through the pupil, which is the black circular opening in the center of the iris. The lens is a clear, flexible structure located behind the iris that helps to focus light onto the retina. The retina is a thin layer of tissue that lines the back of the eye and contains photoreceptor cells called rods and cones. These cells convert light into electrical signals that are sent to the brain via the optic nerve. The rods are responsible for the low light vision and detecting motion, while the cones are ...
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Theories for origin of life on earth

  Theories for origin of life   

Our today's topic is Theories for origin of life, so there are many philosophers and scientists who were tried to explain the origin of life on Earth and give many theories so in this topic we will discuss about these theories and see that from where the thinking of origin of life occurs and and which is the best theory which explain this question properly.So ,lets come and reveal the truth about our blue, living planet earth that how life originated on earth.

1. Theory of special creation:

This is mythology based theory. The greatest supporter of this theory was Father Suarez.
This theory said us that :
(a)  All living organisms that we see today were created as such.
(b)  The diversity was always the same since creation and will be the same in future.
(c)  The earth is about 4000 years old.

But today  we will  know that our earth is not thousands of years old as was thought earlier but billions of years old, from the fossils and their dating, which were obtained from different layer of earth.So, this theory was discarded and all these ideas were strongly challenged during the nineteenth century based on observations of Charles Darwin, Wallace etc.

2. Cosmic panspermia theory:

Some scientists believe that life came from outer space.Early Greek thinkers thought that unit of life called spores were transferred from different planet including earth.But today we know that in space there are many harmful radiations from which not any living entity will survive.So, this theory was also discarded. But 'Panspermia' is still a favourite idea for some astronomers.

3. Theory of Abiogenesis:

This hypothesis was supported by ancient Greek philosophers. According to this theory life came out  of decaying and rotting matter like straw, mud, etc. spontaneously. They believed that the mud of Nile river could give rise to fishes, frogs, crocodiles, etc. when warmed by light rays. This theory was also discarded because we know that there is no magic in the river which could give rise to a whole organism spontaneously.

4. Theory of Biogenesis:

This theory was proposed by Harvey and Huxley. They stated that "omnis vivum ex ovo or vivo" which means " New life can be originated on earth only by pre exiting life".Many experiments were held by different scientists to support the theory of biogenesis and disproved the theory of abiogenesis. In these experiments one famous experiment was the Swan neck flask experiment of Louis Pasteur.

Hence spontaneous generation theory was discarded once and for all. However, our question that how first life origin on earth was yet unsolved.

5. Oparin-Haldane theory (Modern theory):  

This theory was given by Oparin of Russia and Haldane of England. They stated that the first form of life could have come from pre-existing non-living organic molecules (RNA, Protein, etc.) and that formation of life was preceded by chemical evolution.
This is the best theory which explain the origin of first life on earth.
Oparin's theory was published in his book 'Origin of life'.

So hope you will like it, to know the modern theory of origin of life on earth wait for my next post and to see my further post in go on explorediscoveries.blogspot.com

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